Elevator control system



Nov. 2&5, 1968 W. F. GLASER ELEVATOR CONTROL SYSTEM Original Filed Aug. 13, 1952 12 Sheets-Sheet 1 A'rrolaraxsnry *"NNov. 26, 1968 w. F. GLAsER 3,412,826

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ELEVAT OR CONTROL SYSTEM BY ATTORNEY Nov. 26, 1968 w, F, @LASER 3,412,826

ELEVATOR CONTROL SYSTEM BY ATTonNl-:Y

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mL/m maw Asse mveNToR BY ATTORNEY United States Patent "ice 3,412,826 ELEVATOR CONTROL SYSTEM William Frank Glaser, Eastchester, N.Y., assignor to Otis Elevator Company, New York, N.Y., a corporation of New Jersey Continuation of application Ser. No. 304,163, Aug. 13, 1952. This application Jan. 3, 1963, Ser. No. 249,977

32 Claims. (Cl. 187-29) The invention described in this application relates to cont-rol systems for elevators and this application is a continuation of my earlier application Ser. No. 304,- 163, filed Aug. 13, 1952 now abandoned.

The invention is directed primarily to elevator systems in which the cars are operated without attendants, although they may be arranged so that the cars may be operated at certain times with starting under the control of attendants. When operated without attendants, the cars are b-oth started and stopped automatically, the stopping being effected in response to calls registered by passengers and intending passengers themselves. There are certain advantages, especially under certain conditions, in effecting the starting of the cars as well as stopping in response to the calls that are registered. Such systems are known as collective control systems. It is the usual practice in collective control installations yof the multiplex type, i.e., of two or more elevators, to cause landing calls to be lresponded to by one of the cars, but to bring one or more additional cars into operation when certain service Idemand conditions arise. The invention is especially directed to a system for increasing in response to service demands the number of cars in operation.

On feature of the invention is to throw over the system to dispatching, that is automatic starting of the cars on a time basis, when predetermined service demand conditions arise.

This is of advantage in that economical service is provided so long as the service demand is light but that when the demand increases, more cars are provided to answer calls with the cars spaced on a time basis to insure good service.

When operating under dispatching, the number of cars in service may vary. Also, due to changing traffic conditions, the cars may be early Ior late in completing their round trips. Another feature of the invention is to automatically adjust the timing interval in accordance with the number of cars in service or to increase it when a car is late in completing a round trip and decrease it when it is early.

In carrying out the invention according to the preferred arrangement, the system is toperated on an on call basis when traffic demand is light and on a continuous call basis when the demand is heavy. Under on call operation, one of the cars serves as a free car and parks at an intermediate floor. The other cars park at the terminals, one of them at the bottom terminal serving as the active bottom car and taking care of incoming traffic. So long as on call conditions exist, the free car responds to all landing calls until the active bottom car is started in operation by a car call whereupon it assists the free car in responding to landing calls.

When trahie demand conditions warrant, the cars are automatically thrown over to dispatching, being dispatched on a time basis Ion both up and down trips. When all calls are responded to, the cars automatically return to on call operation. In effecting this changeover, a car already at the bottom terminal or, if none, the car first to arrive is selected as the free car and goes to its middle free car parking -oor. The next car at the bottom terminal becomes the active bottom car. Of the remaining cars, one of them is then caused to go to the 3,412,826 Patented Nov. 26, 1968 top terminal as the inactive top car and the remaining car or cars are returned to the bottom terminal as inactive bottom cars.

Other features and advantages of the invention will become apparent from the above statements and from the following description and appended claims.

In the drawings:

FIGURE 1 is a simplified schematic representation of an installation of four elevators in accordance with the invention;

FIGURES 2 and 3 taken together constitute a simplified schematic wiring diagram of continuous call and on call circles for the elevators of FIGURE 1;

FIGURE 4 is a simplified schematic wiring diagram of the hall lantern circuits for one car;

FIGURES 5, 7 and 8 taken together constitute a simplified schematic wiring diagram of power and control circuits for one of the elevators, certain of the circuits being common to the elevators;

FIGURE 6 is a simplified schematic wiring diagram of control circuits for another of the elevators, corresponding to those of FIGURE 5; and

FIGURES 9a to 9e are key sheets for FIGURES 2 to 8, showing the electromagnetic switches in spindle form.

For a general understanding of the invention reference may be had to FIGURE l, wherein is illustrated by way of example a four car elevator installation in which the cars serve ten floors. The floors are designated generally as L and differentiated by appended reference characters. Each car is raised and lowered by means of a hoisting motor 10, which motor drives a traction sheave 11 over which pass hoisting ropes 12 for the car 13 and counter-weight 14. An electromechanical brake 15 is provided and is applied to effect the stopping operation and to -hold the car when at rest.

Each car is provided with a car operating panel 16 on which are located a plurality of control switches for operation by the passengers themselves on without attendant operation and for operation by the car attendant on with attendant operation. These switches include among others a plurality of push buttons, one for each floor above the lower terminal, hereinafter termed car buttons, for registering car calls for both without attendant operation and with attendant operation and a start control button for with attendant operation. Other switches on the operating panel will be referred to later.

Controls are provided at the floors to enable intending passengers to register landing calls, an up control U and a down control D being provided at each intermediate iloor, one control D at the top terminal floor and' `one control U at the bottom terminal floor. Differentiation lbetween these controls is had by appended reference characters. These call registering controls, which will hereinafter be termed landing buttons, are common to the cars and are shown in FIGURE 5.

Referring to the wiring diagrams, FIGURES 2 and 3 are circuits relating to on call and continuous call operations. FIGURE 5 shows the car call registering, car and landing call pick-up, automatic landing call cancelling, farthest car call and farthest landing call circuits for one elevator. This figure also shows the landing call registering circuits which are common to the elevators. Like car call registering circuits, farthest car call circuits and car call pick-up circuits are provided for each of the other elevators as shown in FIGURE 6. As regards the farthest landing call circuits, landing call pick-up and automatic landing call cancelling circuits, like circuits are provide-d for each of the elevators by inter-connection of the selectors as indicated 'by crossconnecting wires WU, WD, WH and WL for the various floors in FIGURES 5 and 6'. FIGURE 4 shows the hall lantern circuits for one car. FIGURE 7 shows control circuits and power circuits for one elevator, it being understood that such circuits are provided also for the other elevators. The circuits of the two columns of FIGURE 2 and yot FIGURE 3 are joined by vertical feed lines W10, W11 and W12.

The feed lines W and W11 supply direct current which may be derived through rectiers from the main source of supply (not shown) when this source is three phase alternating current. Line W10 is the positive side as indicated by the plus sign in FIGURE 2. The feed lines W13 and W14 for the car button circuits of each elevator, see for example FIGURE 5, may be connected to lines W10 and W11 respectively. The feed lines W15 and W16 for the hall lantern and signal circuits of each elevator (see FIGURE 4) may be supplied with single phase alternating current which may Vbe taken from the above mentioned alternating current supply mains, either directly or through a transformer. The lines B-land B of FIGURE 5 supply direct current utilized in the landing button circuits. The primary of transformer TF of FIGURE 5 may be supplied with alternating current from the main source of supply. The secondary of this transformer supplies alternating current utilized in effecting the registration of landing calls and also by Way of line AC1 pulsating current utilized in electing the automatic cancellation of these calls. For convenience line AC1 is not extended down the sheet as in the case of lines B+ and B, but the connections are indicated by applying reference character AC1 to the circuit to which it is connected. The feed lines for the -two columns of circuits of FIGURE 7 are joined by vertical feed lines W17 and W18.

To facilitate disclosure of an application of the invention, the control system illustrated has been considerably simplied as compared with control systems utilized in commercial installations. It is to be understood that in applying the invention to control systems used commercially, many changes may be made, especially in adapting the invention to the more comprehensive circuits and to control features and apparatus not here shown.

The electromagnetic switches employed in the system illustrated are designated as follows:

AB-Active bottom car switch ABC-Group active 'bottom car switch ABD-First auxiliary group active bottom car switch ACT-Automatic time cut-out switch ACX--Auxiliary time cut-out switch AS-A-uxiliary stopping switch ELX-Landing call switch CA-Potential switch CC-Continuous call relay CL*Car late switch DC-Door close switch DCC-Double landing call switch DO-Door open switch EC-Early car switch H-Field and brake switch HCC-Multiple landing call switch HG-Highest car call switch HJ*Highest landing call switch HR-Highest call reversal switch IT-Inactive top car switch ITC- Inactive top car selection switch LA-First late car switch LB-Second late car switch LC-Third late car switch LD-Fourth late car switch LG-Lowest car call switch LI-Lowest landing call switch LNR-Load non-stop relay LR-Lowest call reversal switch LY-Auxiliary main landing return switch MF-Middle :free car switch MFC- Group middle free car switch ML-Main landing switch MR-Main landing return switch NS-Non-stop switch NT-Door time switch PR-Auxiliary reversing switch RA-Running switch SM-Stopping switch TIL-Landing call time switch UD-Direction switch JB-Bottom terminal relay VDL- Down time dispatching `switch VDR-Down selecting switch VSD-Dispatching switch VT--Top terminal relay VITO- Interval throw-over switch VUD-Dispatching change-over switch VULUp time dispatching switch VUR-Up selecting switch WB-Bottom selection `switch WT-Top selection switch XCS-Auxiliary car cut-out relay XIT--Group inactive t-op car switch XM-Interchange switch XSM-Auxiliary stopping switch XTO-Auxiliary interval throw-over switch Throughout the description which follows, these letters will be applied to the coils of the above designated switches. Also, with reference numerals appended thereto, they lwill be applied to the contacts of these switches. The release coil of the electromechanical brake is similarly designated BR. Differentiation will be made between the different elevators by appending to the characters employed to designate the various elements of the system small case letters (1, "b, c and d, indicative of the dilerent elevators.

The circuits are shown in straight, i.e., across-thealine, form in which the coils and contacts of the various switches are separated in such manner as to render the circuits as simple and direct as possible. The relationship of the coils and contacts may be seen from FIGURES 9a to 9e wherein the switches are arranged in alphabetical order with the coils and contacts of the various `switches positioned on spindles. Taking any one of the spindle sheets, each switch thereon has all its contacts and coils on that particular spindle sheet. The coils and contacts are related to the wiring diagrams by applying to the particular coil or contact the num-ber of the gure in which it occurs, this being appended following a dash to the particular designation for the contacts. Each coil and contact is positioned on the spindle sheet in alignment with its position on the particular wiring diagram. Thus a coil or contact of any particular switch may be found by taking the spindle `sheet on which the switch is located, noting the number applied to the coil or following a dash to the contact and aligning that spindle sheet horizontally with the sheet on which the figure indicated is located. The coil or contact will then be found on that ligure in horizontal alignment with that coil or contact on that spindle sheet. For convenience of locating these elements fromI a reading of the specification Without reference to the spindle sheets, the numbers of the figures in which they occur areappended following a dash to both the coils and contacts in the speciication and the wiring diagrams.

The electromagnetic switches are illustrated in deenergized conditions, switches UDa and XTO which are of the latching type being shown in .reset condition. Each of these switches has two coils, one an operating coil and the other a reset coil. Each of switches AB, IT, LA, LB, LC, LD, MF and XM has two coils.

Referring to the landing call registering circuits of FIGURE 5, numerals are appended to the letters U and D for indicating the floors for which the landing buttons are provided. Each of these landing buttons in the preferred arrangement comprises :an electronic tube and a fixed button connected to the tube envelope with the circuits arranged so that the tube breaks down in response to manual touch of the xed button and remains conductive, thereby registering the call and enabling the touch to be discontinued. These electronic tubes are cold cathode gas tubes, the type having a wire anode extending to within a short distance of the glass envelope of the tube, such as the RCA 1G21, having been found satisfactory. (35) H W CLEAVER 16251 NITE PATS NOV 5 With such a tube, the button TB-S, see landing button D3-5, is connected to the tube envelope adjacent the anode. RUL-S and RDL-5 are loading resistors for the tubes. For such tubes, the preferred voltage values are 135 volts from line B-lto line B, 150 volts R.M.S. from line B to the grounded end of the secondary of transformer TF-S and 95 volts R.M.S. 4from line B to line AC1.

It is to be noted that the anode-.cathode circuit of the tube of each landing button is from line B+ lthrough the tube and its load `resistance to line B. The direct current voltage thus applied to the tube is not sufficient to break down the tube. However, upon an intending passenger touching the landing button, a circuit is established from ground GR through the secondary transformer TF to line B which is connected through line B+ to the anode of the tube and thence from the tube envelope by way of the body of the intending passenger back to ground. As a result, suicient alternating current voltage is applied `between the anode and the tube envelope to break down the tube. When the tube fires, it becomes illuminated to indicate that the landing call is registered.

The car buttons for car a are designated Ca-S and, as in the case of the landing buttons, have numerals appended thereto as indicative of the floors for which the -car buttons are provided. Each car button when pressed is held pressed by a magnet CBMa-7 common to these buttons. The starting button in the car is designated SB1a-7. Other -controls are provided on the car panel along with the starting button and car buttons, namely, reversing buttons URBa7 and DRBa-7 for changing the direction of travel at any oor, non-stop button NSBa-7, door open button DOBa-7, and door close button -having double contacts -DCB1a-7 and DCB2a-7. The hall lanterns are designated HLa-4 and differentiated by reference characters corresponding to the floors for which they are provided and by the letters U and D, in accordance with whether up or down hall lanterns. SGa-7 are safety contacts to effect reopening of the doors should anyone step into their paths while closing. SGLa-7 are limit contacts to render contacts SGa-7 ineffective as the doors reach closed position. Resistors are designated generally as R, rectifiers as V and condensers as Q.

Mechanism actuated in accordance with movement of the elevator car is utilized in the circuits of each elevator. Such mechanism may be in the form of a selector machine as indicated in FIGURE l. The selector machine is driven preferably by means of a steel tape 21 attached to the car and counterweight and having teeth formed thereon for engaging teeth on a selector driving wheel 22. The drivin-g wheel acts through bevel gears 23 to drive a vertical screw 24 which in turn drives a crosshead 2S. With this arrangement the crosshead is moved in -accordance with movement of the elevator car. A plurality of contacting elements are carried by the crosshead for engaging stationary elements on oor bars 26, one for each oor.

Referring to the circuits for elevator a in FIGURE 5, one brush CBa-S carried by the crosshead and the stationary contacts CPa-5 with which it cooperates have to do with the car call pick-up operation. Two of the brushes UPBa-S and DPBa-S carried by the crosshead and the stationary contacts UHa-S and DHa-S with which they respectively cooperate have to do with landing call pick-up and automatic call cancelling operations.

A pair of brushes HIBa-S and LJBa-S carried by the crosshead and the stationary contacts HJCa-S and LJCa-S with which they respectively cooperate have to do with farthest landing call circuits. Each of these brushes is mounted on a lever for effecting the separation of contacts when the brush engages a stationary contact, these contacts on the levers being designated HBCa-S and LBCa-5. An isolating cam ICa-S carried by the crosshead and the hook switches HCa-S with which it cooperates have to do with the farthest car call operation. This cam has an upper section of insulating material and a lower section LCSa-S of conducting material. This cam is of a length to engage and open a hook switch for any particular floor slightly ahead of the engagement of the call pick-up brushes with the stationary contacts for that floor when the car is travelling in the up direction and to engage and Open the hook switch for the iioor below such floor ahead of the engagement of the call pick-up brushes with the stationary contacts for such oor when the car is travelling in the down direction. These hook switches are subject to the control of the car buttons and are arranged in series circuit relationship in the farthest car call circuits.

Referring now to FIGURE 4, two additional brushes on the crosshead are for the hall lantern circuits, one for each direction of travel. The up brush is designated ULBa-4 and the down brush is designated DLBa-4. The contacts engaged by brush ULBa-4 are designated generally as ULCa-4 while those engaged by brush DLBa-4 are designated generally as DLCa-4. While these brushes and cams have for convenience been assumed to -rnove in synchronism with the car, it is to be understood that in actual practice they will be in advanced positions, preferably by `moving them to such positions incident to starting the car and returning them to positions cor-responding to car position incident to stopping the car as is Well understood in the art. In FIGURE 7 is a switch DZa-7 which is carried by the crosshead. This switch is actuated by cams (not shown) on the floor bars and is for determining the zone of door operation. Other brushes carried by the crosshead and their cooperating stationary contacts will be referred to later.

A plurality of throw-over switches TO for each car is utilized to provide either without attendant or with attendant operation. Change-over switches CO are also provided in t-he circuits to illustrate certain differences in operation which may Ibe had.

The circuits for controlling the `starting and stopping of car a are shown in FIGURE 7. Any suitable form of power supply may be provided for the elevator motor. One of the preferred arrangements which has been illustrated is to employ a direct current elevator motor and to cause current to be supplied to the motor at a variable voltage, as from a driven generator in accordance with Ward-Leonard principles. The driving motor for the motor generator set has not been illustrated. It is to be understood that either a direct current or alternating current driving motor may be employed, depending upon the kind of power supply to the building and the character of the installation, and that any suitable control arrangement therefor Imay be utilized. An exciter not shown which may be Idriven by the driv-ing motor for the motor generator set may be employed to supply current to feed lines W17a and WlSa and thus to the separately excited iield windings of the supply generator and the elevator motor and to the brake coil and the coils of the various electromagnetic switches of FIGURE 7.

The armature of the generator of the motor generator is designated GAa-7, its separately excited field winding being dlesignlated GFal-7 and its series field winding GSFa-7. The armature of the elevator motor is designated MAa-' and its separately excited field winding EMFa-7. Safety devices are indicated as SDH-7 and are :arranged in circuit with the coil CAa-7 of the potential switch.

The door operating circuits for car a are also shown in FIGURE 7. A hoistway door is provided at `each floor and a door is provided on the car. The car door and hoistway doors have not been shown. A door openating motor is included in the door operating circuits, the motor being carried by the car and actuating both the car door and the hoistway door for the floor at which the car is stopped as is well understood in the art. The armature of the door openating motor is designated DMAa-7 and its eld Winding DMFa-7. Contacts operated by the car door to engage when the door is closed are designated GSa-7. The door contacts operated by the various hoistway doors are arranged in series relation. These contacts are not closed until the doors are closed and locked. For convenience these `door contacts are shown as a single pair of contacts designated DSa-7.

In idescribing the operation of the system, it will lirst be assumed that all cars are on without attendant operation, as indicated by the position of the throw-over switches TO. It will also be assumed that the cars are on on call operation and idle. Under such conditions, switch CC is deenergized as all landing calls have been answered, one clar is parked at a selected intermediate landing, another at the bottom terminal, another at the top terminal and a fourth `at the bottom terminal. The car which is parked at the selected intermediate landing is the middle free car, one of those parked at the bottom terminal is the active botom car, the car parked at the top terminal is the inactive top car, and the other car parked at the bottom terminal is the inactive bottom oar. The selected interl mediate landing which will be termed the middle free car parking iloor will be assumed to be the sixth oor. It will also be assumed that car a has become the middle free car, car b the active bottom car, clar c the inactive top car and car d the inactive bottom car, the cars being illustrated for this conidtion in FIGURE l. The circuits for FIGURE are arranged for parking the middle free car at the sixth floor. However, for convenience and to minimize circuit cross-overs, the circuits for car a are shown for the condition in which the car is at the bottom terminal. It will be understood that with car a parked at the sixth floor, cam ICa-S is in engagement with switch HCGa-S while brushes CBa-S, UPBa-S, DPBa-S, HIBa-S, LJBa-S, and FBa-S are in engagement with their respective sixth iloor stationary contacts. Also, as car a is the middle free car, "its switch MFa is in operated condition. The manner in which the `above operations are etfected will be understood from further description.

The cars park with their doors closed. Iriasmuch as the registration of a landing call for a floor above the bottom terminal starts the middle free car in operation, the circuits for this car will be rst considered. Assume that the car is set for upward travel for which condition switch UDa is latched in operated condition. Also under the assumed conditions a circuit is completed for the coil of switch RAa through contacts HJ1a-7, UD8a-7, CC2a-7, rectifier Vla-7, and switch TO1a-7, causing the switch RA to be operated. Assume now that an intending passenger at the seventh floor touches landing button U75. With the registnation of this call, the potential drop across load resistance RUL'7-5 causes operation of switch HJa, the circuit being from the left-hand side of resistor RUL7-5 through rectifier VHU7-5, rectiers VH7-5 through VHZ-S, contact HlCla-S, brush HlBa-S, rectier VHIa-S, contacts MFZaL-S, coil HIa-S, line B, back to the right-hand side of resistor RUL7-5. Switch HIa separates contacts HJ 1a-7 which, owing to the fact that contacts UD7a-7 are separated, breaks the circuit for the coil of switch RAa. Switch RAa drops out to engage contacts RAM-7. This completes a circuit for the coil of switch Ha, the circuit being through contacts CAla7, NT2a-7, GSa-7, DSa-7, and UD4a-7, terminal stopping switch SSM-7 and contacts RAM-7. Switch Hal operates to engage contacts H7a-7, completing a circuit through contacts UDa-7 and UD14a-7 for generator eld winding GFa-7, and to engage contacts H6a-7, completing a circuit for the release coil BRa-7 of the electromechanical brake. As a result the brake is released and the car is started in the up direction.

Upon the engagement of brush UPBa-S with contact UH7zz-5, a circuit is completed which connects the coil of switch XSMa across loading resistance RUL7-5, the circuit being from the left-hand side of resistance RUL7-5 through contact UH7a-5, brush UPBa-S, contacts PRla-S land NSlzz-S, coil XSMa-S, resistor Rrr-5, to line B, and thus back to the right-hand side of resistor RUL7-5, causing operation of this switch. Switch XSMa engages contacts XSMla-S, completing a circuit through contacts AS2a-5 for the coil of switch SMa. Switch SMa engages contacts SM2a-7 to complete a circuit for the coil of switch NTa. Switch NTw engages contacts NT3a-7 to establish a self-holding circuit. It also engages contacts NTla-S, completing a circuit from the tapped point of the secondary of transformer TF-S through rectifier Vl-S, by way of line AC1, through contacts NTla-S, rectilier V3a-5, contacts NSla-S and PRla-S, brush UPBa-S, and contact UH7a5 to the cathode of the tube of button U7-5. Rectifier V1-5 passes the positive halves ofthe alternating current cycle, thus raising the potential of the cathode with respect to the lanode. This reduces the voltage across the tube to below sustaining value, pulsing out the tube. Thus the up landing call at the seventh tloor is automatically cancelled as soon as the call is picked up. Switch NTcz also separates contacts NT2at-7 which breaks the circuit for the coil of switch Ha. Switch Ha drops out, separating contacts H7a-7 and H6a-7 to break the circuit for generator field winding GFa-7 and the circuit for the brake release coil BRa-7. Thus the bnake is applied and the car is brought to a stop. At the same time contacts H8a-7 engage to connect the generator separately excited field winding to the genator armature with a polarity to oppose the residutal flux of the generator lield.

Switch NTa also engages contacts NT1a-7 which with the closing of switch DZa-7 completes a circuit for the coil of switch DOa. This switch engages contacts DO3a-7 and DO4a-7 to complete a circuit for the armature DMAa-7 of the door operating motor to cause the opening of the doors. As the doors reach open position, limit switch DOL1a-7 opens to deenergze the coil of switch DOa and limit switch DOL2a-7 opens to break the holding circuit for the coil of switch NTa. When switch SMa operated, the engagement of contacts SM2a-7 completed a charging circuit for condenser Q3a-7 connected across coil NTa-7 and the engagement of contacts SM3a-7 completed a charging circuit through contacts XSM1a-7 for condenser Q4a-7 connected across coil NTae7. Thus switch NTa does not drop out immediately its circuit is broken, being delayed by the discharge of condensers Q3a-7 and Q4av7.

Assume that prior to the picking up of the seventh oor call, a down landing call is registered for the ninth iloor. This maintains switch HJa operated and thus switch RAa deenergized when the up seventh oor call is cancelled. Assume further that the passenger who enters the car at the seventh floor desires to be carried to the eighth oor and presses the eighth floor car button C8a-5. The button is held pressed by magnet CBMa-7, the circuit for the magnet being through contact SM1a-7, engaged as a result of the cancellation of the up seventh floor landing call. The car button causes operation of switch HGa, the circuit for coil HGH-5 being through switches HCa-S for the eighth, ninth and tenth floors. Switch HGa engages contacts HG1a-7 to complete a circuit to maintain magnet CBMa-7 energized when an intervening stop is made.

Upon the expiration of the door time interval of switch NTa, contacts NT2a-7 engage to complete the circuit for the coil of switch DCa which engages contacts DC2a-7 and DC3a-7 to cause energization of the door operating motor to effect the closing of the doors. Resistor R6a-7 acts to cause the door closing operation to take place at a slow speed. As the doors reach closed position door close limit switch DCL1a-7 opens to deenergize switch DCa. Also contacts GSa-7 and DSa-7 close to complete the circuit for the coil of switch Ha to effect the restarting of the car.

Upon the engagement of cam ICa-5 with switch HCSa-S the circuit for the coil of switch HGa is broken. However, the car button magnet CBMa-7 is maintained energized through contacts SM1a-7. Thus upon the engagement of brush CBa-S with Contact CPSa-S, a circuit is completed through button CSa-S for the coil of switch SMa, causing the stopping of the car at the eighth floor and the opening of the doors as above described. Also switch SMa separates contacts SM1a7 and inasmuch as the highest car call has been reached so that contacts HG1a-7 are separated, the car button magnet is deenergized to release the car button. This deenergizes switch SMa which reengages contacts SMla-7 to reestablish the car button magnet circuit.

Upon the expiration of the door time interval after the stop at the eighth floor, switch NTa drops out to eifect the reclosing of the doors and starting of the car in the up direction. It is to be noted that, when a stop is effected solely in response to a car button, switch XSMa is not operated and thus condenser 04u-7 is not charged so that a shorter door time interval is provided. Upon the engagement of brush HJBa-S with contact HIC9aS, inasmuch as there is no landing call registered for a oor above the ninth floor and inasmuch as contacts HBCa-S are separated by the engagement of the brush with the contact, the circuit for the coil of switch Hla is broken. The resultant engagement of contacts HI1a-7 completes a circuit through contacts UD8a-7 for the coil of switch RAa. Switch RAa operates to separate contacts RA1a-7, breaking the circuit for the coil of switch Ha, causing the car to be brought to a stop at the ninth floor. At the same time brush LIBa-S engages contact LJC9a-5, with the result that the coil of switch LJa is connected across loading resistor RDL9-5, causing this switch to operate. The resultant engagement of contacts LI2a-7 along with the engagement of contacts Hna-7 completes a circuit for the coil of switch HRa through contacts NT5a-7 and UD12a-7 and switch HRSa-7 (closed because it is olf cam HRCa-7 when the car is away from the main landing). Switch HRa operates to engage contacts HR3a-7, establishing a self-holding circuit. It also separates contacts HRM-7, breaking the circuit for the coil of switch PRa. Switch PRa drops out separating contacts PRla-S and engaging contacts PRZa-S. The engagement of contacts PRZa-S connects the coil of switch XSMa across loading resistor RDL9-5, causing this switch to operate. The resultant engagement of contacts XSM1a-7 completes a circuit for the coil of switch NTa. Thus upon the operation of switch NTa to engage contacts NT1a-5 a circuit is completed through contacts PR2a-'S, brush DPBa-5 and contact DH9a-5 to cause the pulsing out of the tube of the ninth floor landing button, automatically cancelling the call. This results in the dropping out of switch LJa. Switch NTa also effects the opening of the doors as above described. As the stopping of the car is effected, contacts H5a-7 engage to complete a circuit through contacts HR2a-7 and UD9a-7 for the reset coil of switch UDa. This switch is reset, setting the car for downward travel and also separating contacts UD12a-7 to break the holding circuit for the coil of switch HRa.

So long as a landing call is in registration for a tloor above the ymain landing, a circuit is established for the coil of switch BLX, connecting it across the loading resistor or resistors of the tubes upon which landinlg calls are registered. As the down ninth floor landing call is cancelled, no landing calls remain registered so that switch BLX is dropped out. Thus contacts BLXla-S engage, completing a circuit through` contacts MFla-S and BLX1a-5, switches HC6a-5 to HC9a-5, and cam LCSa-5 for the coil of switch LGa. Switch LGa engages contacts LGla-S to complete a circuit for the coil of switch LIa. Switch Lla again operates, separating contacts LJ1a-7. This, with the separation of contacts UDSa-7 as the change in direction is eifected, breaks a circuit for the coil of switch RAa.

Assume that a passenger enters the car and presses fourth floor car button C4a-5. Inasmuch as contacts RAM-7 are now engaged, upon the expiration of the door time interval and closure of the doors, the engagement of door contacts GSa-7 and -DSa-7 causes operation of switch Ha to effect the restarting of the car. The starting of the car is in the down direction as contacts UD'11a-7 and UD13a-7 are now engaged.

Assume that before the car reaches call pick-up distance from the seventh floor a down seventh floor call is registered. This causes operation of switch BLX which separates contacts BLXla-S. The circuit for the coil of switch LGa is maintained however by way of car button 04u-5. Upon the engagement of brush DPBa-S with contact DH7a-5, switch XSMa is operated to cause the stopping of the car at the seventh 4floor and the automatic cancellation of the down seventh floor call. This results in the reengalgement of contacts BLX1a-5. Assume that a passenger enters the car and presses the fifth lloor car button (25a-5. Upon the reclosure of the doors, the car restarts in the down direction. As the car runs past the sixth floor, switch HGa is operated as no landing calls are registered and thus a circuit is completed through contacts MFla-S and BLXlaFS for the coil of this switch. Switch HGaJ engages contacts HGla-S to cause operation of switch HJa. Upon the car reaching call pick-up distance from the fifth floor, the engagement of brush CBa-S with contact CPSaLS causes operation of switch SMa to effect the stopping of the car at the fifth floor. Upon the reclosure of the doors, the car is restarted in the down direction and stopped at the fourth floor in response to the fourth floor car call, the car button being maintained in operated condition until brush CBa-S engages contact CP4a-5 to cause operation of switch SMa to initiate the stop. Since this is the lowest car call, switch LGa is dropped out as a result of the engagement of cam ICal-5 with switch HC-4a-5. Inasmuch as there is no landing call for a floor below, the circuit for the coil of switch LJa is broken upon the engagement of brush LYJBa-S with contact LJC4a-5 to open contacts LCBa-S, contacts LGla-S being separated. Switch Lla engages contacts LI3a-7 which completes a circuit through contacts NT5a-7, switch TO7a1-7, contacts Hl3a7 and UD15a-7 for the coil of switch LRa. This switch engages contacts LR3a-7 to establish a self-holding circuit and engages contacts LR1a-7 to cause operation of s-witch PRa. It also engages contacts LR'Za-7 which, with the engagement of contacts H5a-7, completes a circuit for the set coil of switch UDa, causing operation of this switch to set the car for travel in the up direction.

inasmuch as there are now nocalls remaining to be responded to, the car is returned to the lmiddle free car par-king floor. Incident to the car being brought to a stop at the fourth floor, the engagement of contacts LI1a7 reestablishes the cirouit for the coil of switch lRAa. However, this circuit is broken as soon as the direction of car travel is changed with the resultant separation of contacts UD7a7 inasmuch as contacts HJ1a-7 are separated. Thus upon the expiration of the door time interval and the closing of the doors a circuit is completed for the coil of switch Ha, causing restarting of the car in the up direction. Upon the engagement of cam ICa-S 'with switch HCa-S, the circuit for the coil of switch HGa is broken. Thus, upon the engagement of brush HJBa-S with contact HJC6a-5 to eifect the opening of contacts HBCa-S, the circuit for the coil of switch HJa is broken. This switch drops out to engage contacts HJ 1a-7 completing a circuit for the coil of switch RAa which acts to separate contactsRAlal-7. This breaks the circuit for the coil of switch Ha to cause the car to be brought to a stop at the sixth floor. Inasmuch as there is no call in registration for the sixth floor under the assumed conditions, switch SMa is not operated so that switch NTa is not operated to cause the opening of the doors as the stop is made. It is to be noted if there had been a call for a floor beyond, switch HJa -would have been maintained operated so that the car 'would run past the parking floor without stopping as set forth above.

As each stop is made contacts Hla-S engage to cornplete a circuit for the coil of switch ASa through brush FBa-S and the stationary contact FCa for the particular floor at which the stop is being made. Switch ASa engages contacts ASla-S to become self-holding and separates contacts ASZa-S in the circuit for the coil of switch SMa. This prevents unwanted stopping of the car as it` leaves the floor in response to a late call registered for that floor.

It is believed that it will be understood from the above description that, during upward travel of the car, stops are made in response to calls registered by the car buttons and up landing buttons for floors above the car, in the order in which the floors are reached by the car, regardless of the order in which the calls are registered. Similarly, during downward travel of the car, stops are made in response to calls `registered by car buttons and down landing buttons for floors below the car, in the order in which the floors are reached by the car, regardless of the order in which the calls are registered. Also, during upward travel of the car, a stop may be made at a floor in response to a down landing call, provided no calls are registered for floors above and an up landing call for that floor is not registered to maintain the coil of switch Hla operated. Similarly, during downward travel of the car, a stop may be made at a floor in response to an up landing call provided no calls are registered for floors below and a down landing call has not been registered for that floor to maintain the coil of switch Lla energized. When all calls are responded to, the car automatically returns to the middle free car parking floor where it parks with the doors closed.

As each intervening stop is made during upward travel of the car a circuit is completed, through brush ULBa-4 and the stationary contact ULCa-4 for the floor at which the stop is being made, for the up hall lantern UHLa-4 for that floor. The completion of this circuit is effected by the engagement of contacts NT1a-4 and is maintained through door close limit switch DCLa-4 until the doors reclose. Similar operation is had in the case of each intervening stop during downward travel of the car. In this case the circuit for the down hall lantern DHLa-4 for the particular floor at which the stop is being made is completed through the stationary contact DLCa-4 for that floor, brush DLBa-4 and contacts NT1a-4. Contacts PR1a-4 render brush ULBa-4 effective for up car travel and contacts PR2a-4 render brush DLBa-4 effective for down car travel. When the car in its upward travel stops in response to a down landing call or in response to a car call under conditions where no call is registered for a floor above, the operation of switch HRa causes the dropping out of switch PRa as previously explained. This effects the separation of contacts PR1a-4 and the engagement of contacts PR2a-4 to cause the lighting of the down hall lantern. When the car in its downward travel stops in response to an up landing call or in response to a car call under conditions where no call is registered for a floor below, switch LRa operates to cause reoperation of switch PRa and thus causes lighting of the up hall lantern. When a stop is made at the middle free car parking floor under conditions where no call is in registration for that floor, inasmuch as switch SMa is not operated, switch NTa is not operated and thus contacts NTM-4 do not engage and a hall lantern is not lighted. For convenience, the hall lanterns are not shown in FIGURE 1.

If while the car is parked, an intending passenger, desiring to use the car, touches a landing button, switch XSMa operates to engage contacts XSM1a-7, completing l2 a circuit through contacts Hau-7 and MF1a-7 for the coil of switch NTa. This causes opening of the doors. Also contacts HJla-7 `or LJ 1a-7 separate momentarily to break the circuit for the coil of switch RAa, the dropping out of this switch being delayed by the discharge of condenser Q1a-7 to prevent the starting of the car before the door opening operation is initiated. Thus the intending passenger may enter the car and register a car call for his destination and the car starts upon reclosure of the doors.

Should the car become loaded to a certain percent of capacity, load weighing switch LWSa-7 closes. This switch may be a microswitch operated by the car platform. With switch LWSa-7 closed, upon the operation of switch DCa to initiate the door closing operation, contacts DC1a-7 engage to complete a circuit for the coil of relay LNRa. This relay upon operation engages contacts LNR1a-7 to become self-holding. It also separates contacts LNR2a-7 to effect the deenergization of switch NSa. Thus switch operates to separate contacts NSla-S and NSla-4 and thus prevents the picking up -of landing calls and lighting of hall lanterns until room is again provided in the car by the discharge of passengers. Where a car call stop is made, the separation of contacts DO2a-7 breaks the holding circuit for the coil of relay LNRa, with the result switch NSa is reoperated. This causes automatic cancellation of a landing call, if registered, for the direction in which the car is set to leave the floor.

It will be seen that with the arrangement thus far described the middle free car when idle parks in the middle of the building to be in the best position on the average to take care of interfloor traffic. Incoming traffic is taken care of by the active bottom car parked at the main landing. Assume that an incoming passenger touches up landing button Ul-S at the main landing. This causes operation of switch XSMb to complete a circuit through contacts for car b corresponding to contacts ABM-7 for effecting the opening of the doors for active bottom car b. The doors for the inactive bottom car c are not opened as contacts for car c corresponding to contacts ML1a-7 are separated. Thus the passenger enters car b and presses a car button for his destination. Upon the closure of the doors the car starts in the up direction. During its operation above the main landing, car b assists car a in responding to landing calls, the calls being answered by the car whose landing call pick-up brush for the direction of the call is first to engage its corresponding stationary contact for the floor for which the call is registered. Upon answering its highest call, the active bottom car returns to the main landing. There may be an interchange of cars under such conditions as to which is the middle free car and which is the active bottom car, as will be explained later. Assuming for convenience car b to continue as the active bottom car, a circuit exists through contacts MF3b-6, IT4b-6 and ML2b-6 for the coil of switch MRb, causing this switch to be operated. This switch engages contacts MR1b-6 to complete a circuit through hook switches HCbup to cam LCSb-6 for the coil of switch LGb-6. This switch operates to engage contacts LG1b-6, causing operation of switch LJb. This causes the car upon answering its highest call to be set for downward travel and started in the down direction upon the closing of the doors, as explained for car a. The car answers car calls and down landing calls on its downward trip. Upon returning to the main landing, it parks with its doors closed unless someone enters the car and presses a car button.

When certain service demand conditions arise, the systern is automatically thrown over to continuous call operation. This is effected by causing operation of relay CC. When a landing call is registered for a landing above the main landing, switch BLX is operated to separate contacts BLX1-2, breaking the energizing circuit for the coil of switch TT. This switch is delayed in dropping out by the discharge of condensers Q3-2 and Q4-2, say for one minute, this time depending upon the character- 13 istics of the particular installation. Thus if there is continuous registration of one landing call or overlapping landing calls for this period, switch TI' drops out to engage contacts TT 1-2, completing a circuit through contacts BLX2-2 for the coil of relay CC, causing this relay to operate. Where two landing calls are in registration, switch DCC is operated, causing the separation of contacts DCC1-2 to disconnect condenser Q4-2 from across coil TT-Z, shortening the time interval, say to thirty seconds if the two calls are registered at about the same time and are unanswered before the interval expires. When switch DCC operates it also engages contacts DCCZ-Z to connect condenser Q4-2 across discharge resistor R5-2. Thus if two calls overlap for only a short period, upon the dropping out of switch DCC, condenser Q4v2 is reconnected across coil TT-Z to subject it also to the remaining charge on condenser Q4-2. Should more than two landing calls be registered, say four, switch HCC operates to engage contacts HCCI-Z to cause the immediate operation of relay CC. Should any car be operating automatic load non-stop, the engagement of its LNR1-2 contacts causes the immediate operation of relay CC, provided a landing call is in registration, signified by the engagement of contacts BLXZ-Z, Upon operation, relay CC engages contacts CCZ-Z to establish a self holding circuit and throws over the system to continuous call operation. This operation will now be described.

Relay CC separates contacts CCI-3 to render on call car selection circuits inelective. It also engages contacts CCL-2 to render dispatching circuits effective and engages contacts CCZ-S to cut out switches DCC and HCC. It also operates contacts CC1a-7, CC2a-7 and CC3a-7 to eiect certain changes in the operation of switches RAa and NTa, the same changes being made in the control of these switches for each of the other cars. It also operates contacts CC1a-4, CC2a-4 and CC3a-4 to effect changes in the terminal hall lantern circuits for car a, like changes being made in the hall lantern circuits for each of the other cars. It also engages contacts CCla-S, CC1b-6 and like contacts for cars c and d, causing operation of switches HG for all cars.

The engagement of contacts CCI-2 completes a circuit for the coil of switch VSD for the selected car at each terminal oor to dispatch that car on its trip to the opposite terminal. Under the conditions assumed for operation on on call, this will be car C at the top terminal and car d at the bottom terminal (main landing), car d being the selected car instead of car b. This is due to the fact that car b has been assumed to have left and then returned to the bottom terminal, the selection of car d occurring as car b left as will be explained below. The selection of the cars is controlled by relays VB and VT, switches WB and WT and notching relays of the rotary type designated VUR and VDR.

When car C arrived at the top terminal under the previous assumption, the engagement of its brush SDBC-Z with contact SDTC-2, completed a circuit for the coil of relay VTC. This relay operated to engage contacts VTlc-Z and VT3C-2 and separate contacts VT2c-2. This caused the notching of relay VDR-2 to move its brushes VDRB1-2 and VDRBZ-Z into engagement with contacts VDRClc-Z and VDRC2c-2, the successive notching operations where there is more than one step being etected by the momentary separation of contacts VDRl-Z at the end of each notching step. When contact VDRCZC-Z is engaged, no further notching takes place as contacts VTZC- 2 are separated. The engagement of brush VDRBl-Z with contact VDRCIc-Z completed a circuit through contacts VT1C2 for the coil of switch WTC. This selected car 0. When car b arrived at the bottom terminal under the previous assumption, its brush S'DBb-Z engaged contact SDMb-Z, causing operation of relay VBb to engage contacts VBlb-Z and V-BSb-Z and separate contacts VB2b-2. This caused operation of notching relay VUR to effect operation of switch WBb, this operation being similar to that described for eecting operation of switch WTC. This selected car 17. The later arrival of car d at the lower terminal caused the operation of relay VBd but no further notching took place because contacts VBZb-Z remained separated. However, when car b left the lower terminal in response to the car call, relay VBb dropped out so that relay VUR notched into position to effect operation of switch WBd and thus select car d. This selection was retained when car b returned to the lower terminal as contacts VBZd-Z remained separated.

With switches WBd and WTC operated, contacts WBld- 2 and WT3d-2 are engaged so that upon the engagement of contacts CC1-2 a circuit is completed by way of contacts VULl-Z for the coil of switch VSDd and a circuit is completed by way of contacts VDL3-2 for the coil of switch VSDC. Switch VSDd acts to dispatch car d on an upward trip. Details of the dispatching operation will be given in connection with the circuits for car a upon the arrival of that car at the lower terminal. Switch- VSD@ acts to dispatch car C on a downward trip as will be explained for car a upon its arrival at theupper terminal.

As car d is started on its upward trip, the engagement of its contacts Hld-Z completes a circuit through contacts NTld-Z and WBZd-Z for the coil of switch VUL-2 and for charging condenser Q6-2. As the car moves away from the main floor, brush SDBd-Z moves off contact SDMd-Z, breaking the circuit for the coil of relay VBd. This relay in turn separates contacts VBld-Z, causing the dropping out of switch WBd to separate contacts WB2d-2. This breaks the circuit for the coil of switch VUL-2 which is delayed in dropping out by the discharge of condenser Q6-2 to provide an up dispatching interval. The dropping out of relay VBd causes notching of relay VUR to select another car. This will be car b as it has been assumed to have returned to the main landing and thus its relay VBb is operated. The operation of Switch WBb upon selection of car b, results in the engagement of contacts WB1b-2. Thus upon the engagement of contacts VUL1-2 as switch VUL drops out at the end of the dispatching interval, a circuit is completed for the coil of switch VSDb to cause the dispatching of car b on its upward trip and the reestablishment of the up dispatching interval.

Similar operation is had upon the starting of car c on its downward trip. The engagement of contacts H2c-2 completes a circuit through contacts NTZC-Z and WT 4C- 2 for the coil of switch VDL and for char-ging condenser Q7-Z. As the car moves away from the top landing, brush SDBc-Z moves off contact SDTc-Z, breaking the circuit for the coil of relay VTC. This relay in turn separates contacts VT1C-2, causing the dropping out of switch WTC to separate contacts WT4c-2. This breaks the circuit for the coil of switch VDL-2 which is delayed in dropping out by the discharge of condenser Q7-2 to provide a down dispatching interval.

The next car to arrive at the top terminal is selected as the next to leave. This will probably be car a. When contacts CCI-2 separated as the changeover was effected, they caused the dropping out of switch MFa. Thus contacts MFla-S are separated, opening the circuit for causing return of car a to the middle free car parking oor. Assuming the car is set for upward travel at the time of the changeover, the operation of switch HGa maintains switch HJa operated and thus contacts HI2a-7 separated. This maintains the car set for upward travel. Switch RAa is maintained deenergized by contacts VT1a-7 and VB1a 7 when the changeover is effected. Thus, upon the expiration of the door time interval and the closure of the doors after each stop the car is restarted in the up direction until the top terminal is reached. When this occurs, switch HGa is dropped out by the opening of switch HC10a-5. Switch Hla is maintained operated by way of contacts HBCa-S and MLla-S. Upon the engagement of brush CBa-S with contact CP10a-5, a circuit is completed for the coil of switch SMa, causing the car to be brought to a stop at the top floor. As the Stop is made, contacts Ha-7 engage, completing a circuit through brush RiBa-7, contact RCa-7 and contacts UD9a-7 for the reset coil of switch UDa, causing the car to be set for downward travel. As the car arrives at the top terminal, brush SDBa-Z engages contact SDTa-Z, completing a circuit for the coil of relay VTa. This relay upon operation causes operation of relay VDR. Relay VDR notches into position to cause operation of switch WTa, selecting car a. Thus car a is brought to the top terminal and selected for dispatching. The circuits for controlling the starting of the car in response to the dispatching operation will now be described.

Relay VT upon operation also engages contacts VTla- 7 to complete a circuit through contacts H1a-7, CC1a-7 and VSD1a-7 for the coil of switch RAa. Thus switch RAa is operated and prevents the starting of the car on its downward trip until the down dispatching interval has expired. Incident to this operation, switch RAa engages contacts RA3a-7 to complete a circuit through contacts CC3cz-7 to maintain switch NTa operated and thus the doors in open position until the dispatching interval expires. Switch WTa engages contacts WT1a-4 to complete a circuit for the down hall lantern DHL10a-4 for selected car a, contacts PR2a-4 being engaged incident to setting the car for downward travel. Switch WTa also engages contacts WT3a2 so that upon the expiration of the dispatching interval and consequent engagement of contacts VDL3-2 a circuit is completed for the coil of switch VSDa. This switch operates to separate contacts VSD1a-7 to break the circuit for the coil of switch RAa. This breaks the circuit for the coil of switch NTa causing the closing of the doors and as the doors reach closed position the hall lantern is extinguished and the car is started in the down direction. Switch Ha separates contacts H1a-7 and thus prevents reoperation of switch RAa upon the reengagelment of contacts VSD1a-7 as a' result of the engagement of contacts H2a-2. As the car leaves the floor, switch VTa drops out, separating contacts VT1a-7 in the circuit for coil RAa-7 and separating contacts VT1a-2 to cause the dropping out of switch WTa to restart the dispatching interval.

When car a is started from the top terminal switch LGa is in operated condition, its circuit being through contacts MRla-S, the coil of switch MRa being energized through contacts MFSa-S, IT4a-5 and MLZa-S. Thus switch LJa is operated and contacts LJ3a-7 are separated, preventing the operation of switch LR to change the direction of car travel at the next stop. Switch LGa is maintained operated until cam ICa-S runs onto switch HC1a 5 as the car approaches the bottom terminal. Switch LJa is maintained operated by way of contacts LBCa-S and ITZa-S until the car arrives at the bottom terminal. When brush CBa-S engages contact CPM-5, switch SMa is operated, causing the car to be brought to a stop. As the stop is made, contacts H5a-7 engage, completing a circuit through brush RBa-7 and contact RC1a-7 for the set coil of switch UDa, causing the car to be set for upward travel. Also brush SDBa-Z engages contact SDM@- 2, causing the operation of relay VBa and, if no other car is selected at the bottom terminal, thus the operation of switch WBa to selected car (1. Switch WBa also engages contacts WB1a-4 to cause lighting of up hall lantern UHL1a-4. A-lso relay VBa engages contacts VB1a*7 to cause operation of switch RAa, thus preventing the reclosing of the doors and starting of the car until the dispatching interval has expired. Upon the expiration of the dispatching interval, switch VUL drops out, engaging contacts VUL1-2, completing a circuit through contacts WB1a-2 for the coil of switch VSDa. This switch separates contacts VSD1a-7 to cause the closing of the doors, extinguishing of the hall lantern and starting of the car in the up direction. As the car leaves, switch WBtz drops out to restart the dispatching interval.

Thus it is seen that, under continuous call operation, the cars are selected for dispatching on their up and down trips in the order to their arrival at the terminals. The dispatching operations occur at the expiration of given time intervals. Each car on its upward trip stops at oors for which it has car calls registered and for which up landing calls are registered. Also, each car on its downward trip stops at floors for which it has car calls registered and for which down landing calls are registered. If a car arrives at a terminal before the dispatching interval expires, it waits upon the expiration of the interval. If a car arrives after the interval expires, it is dispatched immediately. An arrangement is provided for automatically adjusting the dispatching interval in accordance with whether the cars are early or late on -a round trip basis. This arrangement will now be described.

As a dispatched car leaves the top terminal for example, contacts WT4-2 for that car separate, breaking the circuit for the coil of switch VDL. The potential across the coil at this instant is the difference in potential between the points Z and X, the potential of point Z ybeing that of li-ne W10 and that of point X being the ratio of resistors R10-2 t0 R9-2 times the potential of line W10. As condenser Q7-2 discharges, the potential of point Z gradually decreases until a point is reached where difference in potential between points Z and X falls below the hold-in voltage of switch VDL which drops out. The timing of the dropping out of switch VUL is effected in a similar manner, the switch dropping out when the potential difference between points Y and X falls to below the hold-in voltage of the switch. Inasmuch as the resistance of the coils of switches VDL and VUL are of high ohmic value as compared with that of resistors R10-2 and R9-2, these resistors may be used for both switches. The potential of point X is determined by the effective amount of resistor R9-2, which is determined by the condition of switches LA, LB, LC and LD, in turn determined by whether the cars are ahead of or behind time.

For convenience, assume that switches LA, LB, LC,

.LD and VTO are in deenergized condition, that switch XTO is in reset condition, and that the next car, say car a, is late in arriving at the top terminal. Under the conditions assumed, the full amount of resistor` R9-2 is included in the timing circuits with the result that a minimum dispatching interval is being provided. During the running of the dispatching interval a circuit exists through contacts VDL2-2 for the coil of switch CL, causing this switch to be operated. When the interval expires, inasmuch as no car is at the top terminal, the separation of contacts VDL2-2 breaks this circuit and switch CL drops out, subject to a slight time delay of a few seconds to provide some leeway. This time delay is provided by the discharge of condenser Q2-2. The resultant engagement of contacts CLI-2 completes a circuit through contacts VTO1-2 for the operating coil of switch LA. This switch operates to engage contacts LA2-2 to establish a circuit through contacts ECI-2 and I C2-2 for the holding coil of switch LA, switch EC being operated because, with no car at the top terminal, contacts WT-2 for each car are engaged. At the same time, contacts CL2-2 engage to complete a circuit through contacts VTO6-2 for the set coil of switch XTO, this switch latching itself in operated condition and engaging contacts XTO2-2.

Upon selection of late car a as it arrives at the top terminal, contacts WT2a-2 complete a circuit for the coil of switch CL. The resultant engagement of contacts CL4-2 completes a circuit through contacts XTO2-2 and ECS-2 for the coil of switch VTO, switch EC being maintained energized by way of contacts VDL1*2 after the selection of car a and consequent separation of contacts WTla-Z. Switch VTO engages contacts VTO7- 2 to establish a self holding circuit. As switch VSDa is .operated as soon as car a is selected, contacts VSDla- 7 separate, deenergizing switch RAa, so that as soon as 

1. A CONTROL SYSTEM FOR A PLURALITY OF ELEVATOR CARS SERVING A PLURALITY OF LANDINGS INCLUDING TERMINAL LANDINGS COMPRISING; CALL REGISTERING MEANS FOR EACH OF SAID LANDINGS; MEANS FOR REGISTERING TRAFFIC CONDITIONS; MEANS RESPONSIVE TO SAID TRAFFIC CONDITIONS REGISTERING MEANS UNDER INTERMITTENT TRAFFIC CONDITIONS FOR CAUSING OPERATION OF ONE OR MORE OF THE CARS ON AN INTERMITTENT BASIS; DISPATCHING MECHANISM FOR THE CARS; AND MEANS RESPONSIVE TO SAID TRAFFIC CONDITIONS REGISTERING MEANS UNDER GREATER TRAFFIC CONDITIONS FOR CHANGING OVER THE OPERATION TO CAUSE THE CARS TO BE DISPATCHED BY THE DISPATCHING MECHANISM FROM AT LEAST ONE OF THE TERMINAL LANDINGS ON A TIME BASIS. 